The insulin receptor has been purified using a combination of wheat germ and receptor antibody affinity chromatography. The receptor antibodies have been used in a new radioimmunoassay for insulin receptors, which is being applied to study receptor phylogeny and function. Lectins are being used as tools to probe receptor function and to purify receptors. Immunoprecipitation of receptors has been used as an assay to screen for receptor antibodies. Low titer IgM antibodies have been found in patients with ataxia-telangiectasia and in the New Zealand obese (NZO) mouse - a model of human adult-type diabetes.